JP2003328102A - Continuous galvanizing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous galvanizing method by which development of defective quality caused by ash in a snout can be prevented. <P>SOLUTION: In the continuous galvanizing method provided with the snout, when the galvanizing is performed by continuously dipping and passing a steel sheet after annealing treatment through molten zinc bath, a movable wall faced to the snout wall at least at the upper surface side of the steel sheet is disposed in the inner part of the snout, and the deposit of the ash onto the inner surface of the snout wall is prevented by shifting the above movable wall. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous melting for preventing quality defects caused by ash generated in a snout during hot dip galvanizing by continuously dipping a steel strip in a hot dip galvanizing bath. The present invention relates to a galvanizing method.

[0002]

2. Description of the Related Art Generally, in continuous hot-dip galvanizing equipment for steel strips, steel strips whose surfaces have been cleaned are continuously annealed, cooled to a predetermined temperature, and then immersed in a hot-dip galvanizing bath (hereinafter also referred to as a plating bath). Galvanize it. Normally, this annealing cooling process is in a reducing atmosphere, and a snout is provided between the furnace equipment and the plating tank for annealing cooling so that the reducing atmosphere can be always secured until the steel strip is immersed in the plating bath. There is a device with a rectangular cross section called, which serves to block the atmosphere.

Further, a sink roll is installed in the plating tank, and the steel strip changes its traveling direction by the sink roll and rises in the vertical direction. The steel strip drawn from the plating bath is adjusted to a predetermined plating thickness by a gas wiping nozzle, then cooled and passed through a post process.

Since the inside of the snout in the above equipment is in a reducing atmosphere, it is difficult to form an oxide film on the plating bath surface inside the snout, and only a thin oxide film is formed. Since the oxide film is not strong on the plating bath surface inside the snout, when the steel strip enters the plating bath, molten zinc may be exposed on the bath surface due to vibration or the like. in this case,
Molten zinc in the liquid phase evaporates into the reducing atmosphere gas up to the saturated vapor pressure of the molten zinc being heated.

The vaporized molten zinc vapor reacts with a small amount of oxygen present in the reducing atmosphere gas to form an oxide,
It adheres to the cooling furnace part in the furnace and the inner wall of the snout. Even if it does not become an oxide, if the vapor pressure of the vaporized molten zinc exceeds the saturated vapor pressure at that location, the vaporized molten zinc cannot exist in the vapor state. Phase change to zinc. In the cooling furnace part and the snout in the furnace, when the temperature is below the saturation temperature in the vapor pressure of the evaporated molten zinc, zinc vapor easily becomes powdery zinc and adheres at the temperature below that temperature. .

A mixture of the oxide and powdery zinc is called ash, and the ash adheres to the inside of the furnace and the inner wall of the snout. During operation, if the adhered and accumulated ash falls on the cleaned steel strip and adheres to it, the plating becomes non-uniform and the non-plating state occurs, resulting in quality defects. Since ash does not redissolve in the plating bath,
Ash falling on the bath surface floats on the bath surface. If this ash is rolled up and attached to the steel strip to be passed, the above-mentioned quality defects will occur.

Many methods have been proposed in the past for preventing the occurrence of quality defects caused by ash during hot dip galvanizing. For example, Japanese Patent Laid-Open No. 7-62512 discloses a method of suspending a ceramic ball on the surface of a snout bath to reduce zinc vapor. Further, JP-A-8-302453 discloses a method of sucking a gas in a snout containing zinc vapor with a blower and discharging the gas out of the system.

[0008]

However, Japanese Patent Laid-Open No. 7-6
The method proposed in Japanese Patent No. 2512 is concerned about various problems such as generation of defects due to mixing ceramic balls in the bath. Further, in the method proposed in JP-A-8-302453, by discharging a gas containing zinc vapor to the outside of the system, the zinc vapor pressure in the snout becomes small, and the evaporation amount of zinc from the bath surface increases. To do. Therefore, it is difficult to completely eliminate zinc vapor in the snout, and as a result, ash formation on the inner wall of the snout is unavoidable.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a continuous hot dip galvanizing method capable of preventing the occurrence of quality defects caused by ash in a snout.

[0010]

The means of the present invention for solving the above problems are as follows. (1) In a continuous hot-dip galvanizing facility equipped with a snout, when the annealed steel strip is continuously immersed in a hot-dip galvanizing bath for hot-dip galvanizing, the snout wall at least on the upper surface of the steel strip inside the snout. A movable wall is installed so as to be opposed to the movable wall, and the movable wall is moved to prevent the accumulation of ash on the inner surface of the snout wall (first invention).

(2) In (1), the movable wall is moved in the steel strip passing direction, and the ambient gas between the movable wall and the snout wall is forced to flow by the accompanying flow caused by the movement of the movable wall. A continuous hot dip galvanizing method (second invention).

(3) In the above (1), the movable wall is moved in a direction opposite to the steel strip passing direction, and the ambient gas between the movable wall and the snout wall is generated by the accompanying flow due to the movement of the movable wall. A continuous hot-dip galvanizing method characterized by forced flow (third invention).

(4) An opening is provided at an upper end of the movable wall or a snout portion near the upper end of the movable wall, and the gas in the snout is discharged from the opening to the outside of the snout. Hot-dip galvanizing method (4th invention).

(5) An opening is provided in the snout side wall portion near the lower end of the movable wall or in the vicinity thereof, and the gas in the snout is discharged to the outside of the snout through the opening. Continuous hot dip galvanizing method (fifth invention).

(6) Ash is removed from the gas discharged to the outside of the snout for cleaning, and the cleaned gas is introduced into the snout from the inlet provided in the snout portion at the lower end of the movable wall or in the vicinity thereof. (4) characterized in that
The continuous hot-dip galvanizing method described in (6th invention).

(7) Ash is removed from the gas discharged to the outside of the snout for cleaning, and the cleaned gas is introduced into the snout from an inlet provided in the snout portion at or near the upper end of the movable wall. (5) characterized in that
The continuous hot dip galvanizing method described in (7th invention).

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various investigations and studies in order to prevent quality defects caused by ash generated in snouts. As a result, the ash locally adheres to and deposits on the inner wall of the lower part of the snout, especially on the inner wall of the snout near the bath surface.Large ash separates from this part and drops directly onto the steel strip surface. By doing so, it became clear that quality defects caused by ash occur particularly remarkably. Even if it does not fall directly on the surface of the steel strip, the ash that has fallen above floats on the bath surface and adheres to the steel strip that is threaded through the ash, causing a quality defect due to ash. Also became clear.

Then, the ash is the inner wall of the snout,
In particular, by preventing local adhesion and deposition on the inner wall of the snout near the bath surface, it is possible to effectively prevent the occurrence of quality defects due to ash. It is effective to install a movable wall facing the snout wall and move the movable wall, and forcibly flow the atmospheric gas between the movable wall and the snout wall by the accompanying flow of the movement of the movable wall. Has been found to be more effective. The present invention is based on this finding.

According to the first aspect of the present invention, in a continuous hot dip galvanizing facility equipped with a snout, when the steel strip after the annealing treatment is continuously dipped and passed through a hot dip galvanizing bath for hot dip galvanizing, the steel strip surface inside the snout is The movable wall is installed so as to face the snout wall on the side opposite to, and the movable wall is moved. The lower end of the movable wall is installed so as to be located near the bath surface on the bath surface.

The movable wall may be reciprocated in a predetermined direction for a predetermined distance. However, from the viewpoint of preventing ash from locally adhering to and depositing on the inner wall portion of the lower part of the snout,
It is preferable that the movable wall is constituted by an endless belt, and the endless belt travels in the steel strip passing direction or in a direction opposite to the steel strip passing direction. Due to the forced flow of the atmospheric gas between the endless belt and the snout wall due to the accompanying flow of the moving wall movement, local adhesion and deposition of ash on the inner wall of the snout near the plating bath surface is suppressed. .

It is important to prevent the ash from directly falling on the surface of the steel strip, since the quality of the ash is greatly affected when the ash directly falls on the surface of the steel strip. The movable wall may be installed so as to face the snout wall on the side facing the upper and lower surfaces of the steel strip, but from the above viewpoint, the movable wall needs to be installed so as to face at least the snout wall on the upper surface side of the steel strip. Is.

In the second aspect of the invention, in the region between the movable wall and the snout wall, the accompanying flow of the movable wall is a downward flow. In this area, zinc vapor evaporated from the plating bath surface is confined to the bath surface, so that zinc vapor is prevented from directly flowing into this area, and the atmosphere gas in the area between the movable wall and the snout wall is It is forced to flow by the accompanying flow of. as a result,
At the snout wall portion, the ash is prevented from locally adhering to the portion near the bath surface.

In the third aspect of the invention, the flow of the atmospheric gas becomes an upward flow in the region between the snout wall and the movable wall, and the flow of the atmospheric gas becomes a downward flow in the region between the steel strip and the movable wall. Due to this flow, the portion near the bath surface of the snout wall is agitated, and the zinc vapor evaporated from the plating bath surface flows upward in the region between the movable wall and the snout wall by this flow.
Since the region is forced to flow by the accompanying flow of the movable wall, it is possible to prevent the ash from locally adhering to the snout wall.

In the first to third inventions, the ash is prevented from locally adhering to and depositing on the inner wall portion of the snout below the snout, so that large ash is prevented from peeling off from the portion. The occurrence of quality defects is prevented.

The present inventors investigated the occurrence of ash adhesion to the snout wall by forming the movable wall with an endless belt and changing the rotating direction and rotating speed of the endless belt. As a result, in a normal continuous hot-dip galvanizing equipment, the moving speed of the movable wall (rotating speed of the endless belt) is 0 m / m irrespective of the rotating direction of the endless belt.
In the range of more than s and less than 0.5 m / s, ash was generated due to insufficient forced flow of the atmospheric gas between the steel strip and the movable wall, but local ash was found in the snout part near the plating bath. It was confirmed that there was no adhesion. The speed is 0.
It was confirmed that forced flow occurred at 5 m / s or more, and ash adhesion to the snout wall surface was averaged as the speed increased. It was also found that it is desirable that the moving speed of the movable wall be equal to or higher than the steel strip passing speed. Therefore, the moving speed of the movable wall is preferably 0.5 m / s or more, more preferably the steel strip passing speed or more.

From the viewpoint of preventing the occurrence of quality defects due to ash, it is more preferable that the amount of ash generated in the snout is small. In the fourth invention and the fifth invention, by discharging the gas in the snout to the outside of the snout,
Zinc vapor, zinc oxide, zinc powder, etc. contained in the gas are discharged together. Zinc vapor, which leads to ash formation
By discharging oxides, zinc powder, etc. out of the system, the amount of ash generated in the snout is reduced. as a result,
The inside of the snout is cleaned, and the effect of preventing the occurrence of quality defects due to ash is more excellent.

In the sixth invention and the seventh invention, the ash is removed from the gas discharged to the outside of the snout for cleaning, and the cleaned gas is introduced into the snout. By doing so, the amount of ash generated in the snout is reduced, and the inside of the snout is cleaned, so that the effect of preventing the occurrence of quality defects due to ash is more excellent. Also, ash will not be released into the atmosphere.

According to experiments conducted by the present inventors, in the normal continuous hot-dip galvanizing equipment, in the fourth to seventh inventions, the amount of gas discharged to the outside of the snout is the flow rate conversion (flow rate / flow rate / flow rate) in the snout portion. Cross section) 0.4m
It is preferable to set the flow rate to be not less than / s.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a main part of a continuous hot-dip galvanizing facility including a movable wall.
In FIG. 1, S is a steel strip, 1 is an annealing furnace, 2 is a snout,
3 is a plating tank, 3a is a plating bath (molten zinc bath), 4 is a sink roll, 5 is a collecting roll, 6 is a stabilizing roll, 7 is a gas wiping nozzle, and 8 is a touch roll.

In the equipment shown in FIG. 1, an endless belt 9 and an upper roll 10 and a lower roll 11 for rotationally driving the endless belt 9 are further provided on the upper surface side and the lower surface side of the steel strip S inside the snout 2, respectively. is set up. The endless belt 9 constitutes a movable wall, and is arranged substantially parallel to the inner wall of the snout and the steel strip surface. The portion of the endless belt 9 installed on the upper surface side of the steel strip S on the side facing the snout wall 2t on the upper surface side of the steel strip S is disposed close to the snout wall 2t,
The portion of the endless belt 9 installed on the lower surface side of the steel strip S on the side facing the snout wall 2b is arranged close to the snout wall 2b. The lower end of the endless belt 9 is installed at a position near the surface of the plating bath that does not come into contact with the plating bath, and the rotation direction of the endless belt 9 is configured to be rotatable in the forward and reverse directions. The distance between the endless belt 9 and the snout walls 2a, 2b is preferably about 50 mm or more from the viewpoint of preventing the two from contacting each other.

The steel strip S annealed in the annealing furnace 1 by a conventional method using the equipment shown in FIG. 1 is continuously dipped in the plating bath 3a through the snout 2 and pulled up from the plating bath 3a, and the gas wiping nozzle 7 is used. Adjust the coating weight with.

At this time, the endless belt 9 is driven by the driving device.
By rotatively driving (that is, moving the movable wall) (not shown), ash does not adhere to or accumulate on the endless belt 9 itself. Since the belt 9 moves near the snout wall 2a or 2b portion of the snout 2, the local accumulation of ash is mechanically suppressed in the portion near the bath surface of the snout wall 2a or 2b portion of the snout 2. To be done. As a result, quality defects caused by ash locally attached to the inner wall of the snout near the bath surface are prevented.

FIG. 2 shows the equipment shown in FIG. 1 so that the moving direction of the portion of the endless belt 9 on the snout wall 2t, 2b side is the same as the passing direction of the steel strip S (ie,
It is a figure explaining the gas flow in the snout 2 when the endless belt 9 is rotationally driven so that the moving direction of the portion of the endless belt 9 on the steel strip S side is opposite to the steel strip passing direction. In the figure, the dotted arrow indicates the belt rotation direction, the solid arrow indicates the traveling direction of the steel strip S, and the flow direction of the furnace gas (atmosphere gas) in the region between the steel strip S and the endless belt 9. In the present specification, when the portion of the endless belt 9 on the side of the steel strip S moves in the direction opposite to the steel strip passing direction, as shown in FIG.

When the steel strip S is passed through the snout 8, the atmospheric gas is accompanied by the steel strip S into a downward flow moving in the bath surface direction in the region between the steel strip S and the endless belt 9, and When it collides with the surface, it reverses and becomes an upward flow that moves upward together with the endless belt 9 rotating outward. In the region between the endless belt 9 and the snout wall, the zinc vapor evaporated from the plating bath surface is contained in the bath surface, so that the zinc vapor does not directly flow into the region.

The zinc vapor evaporated from the plating bath 3a moves above the endless belt 9 by the upward flow. The zinc vapor that has moved above the endless belt 9 becomes zinc oxide or solid-phase zinc (zinc powder) during the movement process or after the movement, or remains as zinc vapor. These flow downward from the region between the steel strip S and the endless belt 9 due to the flow of the atmosphere gas (a part further flows to the upstream side of the snout (the direction opposite to the steel strip passing direction)). In the region between the endless belt 9 and the snout wall, the moving endless belt 9 forcibly flows the atmospheric gas, so that the ash made of zinc oxide, solid-phase zinc, or the like adheres to the snout wall surface on average, and Local adhesion and deposition on the inner wall surface of the snout near the bath surface is prevented.

From the viewpoint of enhancing the effect of preventing the ash from adhering to the wall surface of the snout by forcibly flowing the atmospheric gas, the rotation speed of the endless belt is preferably 0.5 m / s or more, and the steel strip threading speed or more. More preferably.

In the above, the amount of ash produced in the snout itself is not reduced. From the viewpoint of preventing the occurrence of quality defects caused by ash, it is desirable that the amount of ash generated in the snout itself be reduced. The amount of ash generated in the snout can be reduced by providing an opening in the snout portion and discharging the in-furnace gas containing ash such as zinc vapor, zinc oxide, and zinc powder from the opening to the outside of the snout.

FIG. 3 shows an example of an apparatus in which an opening 21 for discharging the gas in the snout to the outside of the snout is provided in the snout portion. The openings 21 are provided on both side walls of the snout near the upper end of the endless belt 9 in the direction of the end of the steel strip. Further, the openings 21 are connected with a pipe 22 having a pipe portion 22a which is vertically erected. ing. 24 is a valve. By providing the opening 21 at the above position, the gas in the snout containing zinc vapor, zinc oxide, zinc powder, etc. is effectively discharged to the outside of the system (outside the snout).

In the equipment of FIG. 1, the internal pressure between the annealing furnace 1 and the snout 2 is maintained at a positive pressure. Therefore, in the apparatus shown in FIG. 3, due to the difference between the furnace pressure and the atmospheric pressure and the draft effect of the pipe 22 (so-called stack effect), the furnace gas containing zinc vapor, zinc oxide and zinc powder discharged from the opening 21 is It is released into the atmosphere, and the atmosphere (oxygen) snouts 2
Inflow is prevented. According to the device of FIG.
Although it is a simple device, the ash such as zinc vapor, zinc oxide, and zinc powder in the snout 2 can be effectively used.
Since it is discharged to the outside, the amount of ash generated in the snout 2 itself is reduced and the inside of the snout 2 is cleaned.

The position of the opening 21 is preferably the position shown in FIG. 3, but the position is not limited to this position. The opening is, for example,
You may provide in the part on the side which opposes the steel strip surface of the snout 2. In this case, the opening 21 is preferably provided in the snout portion above the upper end of the endless belt 9. The shape of the opening may be circular, rectangular, or slit-shaped.

In the apparatus shown in FIG. 3, the gas discharged from the opening 21 was diffused into the atmosphere, but the apparatus shown in FIG. 4 was used to remove zinc vapor from the gas discharged outside the snout.
By removing oxides, zinc powder and the like to clean the gas and introducing the cleaned gas into the snout, the ash may be prevented from being released into the atmosphere.

In FIG. 4, 31 is a gas outlet, 32 is a cleaner (purifier) equipped with a filter, 33 is a fan, 34 is a gas inlet, and 35 is a pipe. The gas discharge ports 31 are provided on both side wall portions in the width direction of the steel strip of the snout 2 near the upper end of the endless belt 9 (near the upper roll 10). The gas introduction ports 34 are provided in both side wall portions in the steel strip width direction of the snout 2 near the lower end of the endless belt 9 (near the lower roll 11).

The fan 33 sucks in-furnace gas containing zinc vapor, oxides, solid-phase zinc, etc. from the gas outlet 31, passes through the cleaner 32, and zinc vapor contained in the gas,
Solid phase zinc, oxides, etc. are removed as ash and cleaned. The purified gas is introduced into the snout 2 through the gas introduction port 34. As a result, the amount of ash generated in the snout 2 is reduced and the inside of the snout 2 is cleaned. Also, ash is not released into the atmosphere.

The installation locations of the gas outlet 31 and the gas inlet 34 are not limited to the positions shown in FIG. Gas outlet 3
The installation location and shape of 1 can be the same as the opening 21 described in FIG. The gas inlet 34 may be provided in a portion of the snout 2 that faces the steel strip surface.
The shape may be circular or rectangular, or may be slit-like.

The case where the endless belt 9 is rotated outward has been described above with reference to FIGS. Next, the case where the endless belt 9 is rotated in the opposite direction will be described.

FIG. 5 shows that in the equipment shown in FIG. 1, the portions of the endless belt 9 on the side of the snout walls 2t, 2b move in the direction opposite to the passing direction of the steel strip S (that is, the steel of the endless belt 9). It is a figure explaining the gas flow in the snout 2 when the endless belt 9 is rotationally driven so that the part on the strip S side moves in the same direction as the steel strip passing direction. In FIG. 5, dotted arrows indicate the rotation direction of the endless belt 9, solid arrows indicate the traveling direction of the steel strip S, and the flow direction of the furnace gas (atmosphere gas) in the region between the steel strip S and the endless belt 9. In this specification, when the portion of the endless belt 9 on the side of the steel strip S moves in the same direction as the steel strip passing direction, as shown in FIG.

When the steel strip S is passed through the snout 8, the atmosphere gas is bathed in the region between the steel strip S and the endless belt 9 along with the steel strip S and the inwardly rotating endless belt 9. Move in the plane direction.

In the region between the snout wall surfaces 2t, 2b and the endless belt 9, the gas containing zinc vapor rises along with the endless belt 9. Since the endless belt 9 is rotating, the atmospheric gas is forced to flow in the region between the snout wall surfaces 2t, 2b and the endless belt 9, so that zinc oxide and zinc powder are attached to the snout wall surface evenly, and Local adhesion and deposition on the inner wall surface is prevented.

From the viewpoint of preventing the occurrence of quality defects due to ash, it is desirable to be able to reduce the amount of ash produced in the snout itself. In this case, however, the lower end of the endless belt 9 or its vicinity (the vicinity of the lower roll 11). ), An opening is provided in the snout portion, and the in-furnace gas containing zinc vapor, zinc oxide, and zinc powder is discharged from the opening to the outside of the snout, thereby reducing the amount of ash generated in the snout. Are cleaned.

FIG. 6 shows an example of an apparatus in which an opening 21a is provided in a snout portion near the lower end of the endless belt 9.
In the apparatus of FIG. 6, the openings 21a are provided in both side wall portions of the snout 2 on the side of the steel strip end, and the openings 21a are vertically erected similarly to the case of the apparatus of FIG. A pipe 23 having a closed pipe portion 23a is connected. Two
4 is a valve.

In the apparatus shown in FIG. 6, as in the case of the apparatus shown in FIG. 3, zinc vapor, zinc oxide and solids are discharged from the opening 21a due to the difference between the furnace pressure and the atmospheric pressure and the draft action (chimney effect) of the pipe 23. Gas in the snout containing phase zinc is diffused into the atmosphere and the atmosphere is prevented from flowing into the snout. As a result, the amount of ash generated in the snout 2 itself is reduced and the inside of the snout 2 is cleaned.

The position of the opening 21a is not limited to the position shown in the apparatus of FIG. The opening 21a may be provided, for example, on the side facing the steel strip surface of the snout 2. Opening 2
The shape of 1a may be circular or rectangular, or may be slit-like.

Further, by using an apparatus as shown in FIG. 7, ash such as zinc vapor, zinc oxide and zinc powder is removed from the gas discharged to the outside of the snout 2 for cleaning, and the cleaned gas is snouted. It may be returned to within 2.

In FIG. 7, 31a is a gas outlet, and 32 is a gas outlet.
Is a cleaner, 33 is a fan, 34a is a gas inlet, 3
6 is a pipe. The gas discharge ports 31 are provided on both side wall portions in the steel strip width direction of the snout 2 near the lower end of the endless belt 9 (near the lower roll 11). This allows zinc vapor. Gas containing zinc oxide, zinc powder, etc. is effectively discharged out of the system. The gas introduction ports 34 are provided on both side wall portions in the steel strip width direction of the snout 2 near the upper end of the endless belt 9 (near the upper roll 10).

In the fan 33, the in-furnace gas containing zinc vapor, zinc oxide, and solid-phase zinc is sucked from the gas outlet 31, passes through the cleaner 32, and zinc vapor, zinc powder, and oxides contained in the gas. Etc. are removed as ash and cleaned. The purified gas is supplied through the gas inlet 34
Introduced into Snout 2. As a result, the amount of ash generated in the snout 2 is reduced and the inside of the snout 2 is cleaned. Also, ash is not released into the atmosphere.

The installation locations of the gas outlet 31a and the gas inlet 34a are not limited to the positions shown in FIG. The location and shape of the gas outlet 31a can be the same as that of the opening 21a described in FIG. Gas inlet 3
The installation place of 4a may be provided on a portion of the snout 2 that faces the steel strip surface. The shape may be circular, rectangular, or slit-like.

In the apparatus shown in FIGS. 3 and 6, the flow rate of the gas discharged to the outside of the snout can be adjusted by the opening, the dimension of the pipe, the valve opening and the like. Further, in the apparatus shown in FIGS. 4 and 7, the flow rate and flow rate of the atmospheric gas circulating between the snout and the cleaner can be adjusted by the rotation speed of the fan and the dimensions of the gas outlet and the gas inlet.

Further, in the apparatus described above, the movable wall is installed so as to face each of the snout walls facing both sides of the steel strip, but the movable wall faces the side facing the upper surface of the steel strip as necessary. It may be provided only in.

[0059]

As described above, according to the present invention, the ash is prevented from locally adhering to the inner wall surface of the snout by installing and moving the movable wall surface in the snout. It is possible to prevent quality defects caused by

Further, in the fourth invention to the seventh invention, since the ash generated in the snout is reduced and the inside of the snout is cleaned, the above effect is more excellent.

In the fifth and seventh inventions, ash is further prevented from being diffused into the atmosphere.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a main part of a continuous hot-dip galvanizing facility including a movable wall referred to in the description of the embodiment of the present invention.

2 illustrates the gas flow in the snout when the endless belt is rotationally driven so that the part on the snout wall side of the endless belt is in the same direction (outer rotation) as the steel strip passing direction in the equipment of FIG. 1. FIG.

FIG. 3 is a schematic view showing a configuration example of an apparatus in which an opening for discharging gas in the snout is provided in a snout portion when the endless belt rotates as shown in FIG.

FIG. 4 is a schematic diagram showing a main part configuration of an apparatus for cleaning gas discharged from the nout when the movable wall surface is operated outward and introducing the cleaned gas into the snout.

5 illustrates the gas flow in the snout when the endless belt is rotationally driven so that the portion on the snout wall side of the endless belt is in the opposite direction (inward rotation) to the passing direction of the steel strip in the equipment of FIG. 1. FIG.

FIG. 6 is a schematic diagram showing a configuration example of an apparatus in which an opening is provided in a snout portion near an upper end of the endless belt when the endless belt rotates as shown in FIG.

FIG. 7 is a schematic diagram showing a main part configuration of an apparatus for cleaning gas discharged from a snout when a movable wall surface is operated inward and introducing the cleaned gas into the snout.

[Explanation of symbols] S steel strip 1 Annealing furnace 2 snouts 3 plating tank 3a Plating bath (hot dip zinc bath) 4 Syncroll 5 collecting rolls 6 Stabilizing roll 7 gas wiping nozzle 8 touch roll 9 Endless belt (movable wall) 10 top roll 11 Lower roll 21, 21a opening 22, 22a, 23, 23a Piping 24 valves 31, 31a outlet (gas outlet) 32 Cleaner 33 fans 34, 34a Inlet port (gas inlet port) 35, 36 piping

Claims (7)

[Claims] 1. In a continuous hot-dip galvanizing facility equipped with a snout, at the time of hot dip galvanizing by continuously dipping the annealed steel strip in a hot-dip galvanized bath, at least the upper surface side of the steel strip inside the snout. A continuous hot dip galvanizing method, characterized in that a movable wall is installed so as to face the snout wall, and the movable wall is moved to prevent the accumulation of ash on the inner surface of the snout wall. 2. The movable wall according to claim 1, wherein the movable wall is moved in the steel strip passing direction, and the atmospheric gas between the movable wall and the snout wall is forcedly flowed by the accompanying flow due to the movement of the movable wall. And a continuous hot dip galvanizing method. 3. The movable wall according to claim 1, wherein the movable wall is moved in a direction opposite to the steel strip passing direction, and the ambient gas between the movable wall and the snout wall is forcedly flowed by the accompanying flow caused by the movement of the movable wall. A continuous hot-dip galvanizing method, which comprises: 4. An opening is provided in a snout portion at or near an upper end of the movable wall, and gas in the snout is discharged from the opening through the opening.
The continuous hot-dip galvanizing method described in 1. 5. The continuation according to claim 3, wherein an opening is provided in a snout side wall portion near the lower end of the movable wall or in the vicinity thereof, and the gas in the snout is discharged to the outside of the snout through the opening. Hot dip galvanizing method. 6. The ash is removed from the gas discharged to the outside of the snout for cleaning, and the cleaned gas is introduced into the snout through an inlet provided in the snout portion at or near the lower end of the movable wall. The continuous hot-dip galvanizing method according to claim 4, wherein. 7. The ash is removed from the gas discharged to the outside of the snout for cleaning, and the cleaned gas is introduced into the snout from an inlet provided in the snout portion at or near the upper end of the movable wall. The continuous hot dip galvanizing method according to claim 5, wherein